Black swan (Cygnus atratus)

The black swan is the state emblem of Western Australia, and appears on the state flag.

When in flight, a group of black swans is known as a ‘wedge’, whereas on the ground it is known as a ‘bank’.

The black swan’s scientific name means ‘a swan attired in black’, and refers to this large waterbird’s sooty-black plumage.

The black swan is known to make a variety of high-pitched, musical baying, bugling and trumpeting calls.

The black swan is classified as Least Concern (LC) on the IUCN Red List (1).

One of just three swan species found in the southern hemisphere (4), the black swan (Cygnus atratus) is a large and unmistakable waterbird. Its scientific name means ‘a swan attired in black’ (5), and refers to the species’ almost entirely black plumage (3) (4) (6) (7) (8). The sooty-black feathers are fringed with grey, especially on the upperparts (3), and the raised, ‘crinkly’ wing feathers give this bird’s closed wing a somewhat ruffled appearance (3) (6).

While the black swan has mostly black plumage, its outer primary and secondary feathers are white. These feathers are largely concealed when the bird has its wings folded, but are conspicuous in flight (2) (3) (6) (7) (8). During the annual moult after the breeding season, the white wing feathers are shed, leaving the black swan unable to fly for about a month or so (3) (7).

In proportion to its size, the black swan has the longest neck of any swan species (3) (7). This long, slender neck (6) is often arched in an ‘S’ shape or held erect, and this species often carries its wings raised in an aggressive display (7). The black swan’s bill is a bright, waxy red with a pale bar and tip (3) (6) (7) (8), and a patch of bare, red skin extends back from the bill to the reddish eyes (2) (3) (6). The legs and feet of the black swan are black (3) or greyish-black (7).

The female black swan is very similar to the male in appearance, but the female tends to be smaller (2) (3) (7), with a duller (2) (3), shorter bill (7). Juvenile black swans are brown and mottled greyish (2), with light-tipped feathers, paler underparts, and a paler bill than the adult birds (2) (3).

The black swan is a strong flier, and when travelling together individuals can be seen forming a line or a ‘V’ shape, their wings making whistling noises as they beat slowly (7). In flight and on the water, the black swan is known to make a variety of high-pitched, musical baying, bugling or trumpeting calls (3) (7) (8). This species is also reported to utter a range of softer crooning notes, and tends to whistle when disturbed while nesting (7).

The black swan is native to Australia, including Tasmania (2) (3) (7) (9). It mainly occurs in the wetlands of south-western and south-eastern Australia (7), and is not usually found in the extreme north or in central deserts (3) (7).

Following the extinction of a subspecies of the black swan in New Zealand due to hunting (7), the Australian black swan was introduced to the country, and has since become well established (2) (3) (7). Some black swans have also flown to New Zealand and recolonised the country naturally (7) (9).

The black swan has also been introduced to Singapore (9), and is popular in Western Europe as an ornamental waterbird, particularly in Britain, where some escapes have been recorded (7). This species is known to be a vagrant in Indonesia (9), as well as in New Guinea (2).

The majestic black swan occurs in a variety of wetland habitats, including large lakes, lagoons, swamps and ponds (2) (3) (8), particularly those that are relatively shallow (2) and those with underwater and emergent vegetation for food and nesting materials (7). This species can be found in both freshwater and brackish areas (2) (3) (7). While the black swan tends to prefer permanent bodies of water (2), it can also be found in flooded pastures, tidal mudflats and other areas with temporary flooding (3) (7).

Outside of the breeding season, the black swan occurs in an even greater variety of habitats (2), including saltwater lakes (7), salt marshes (10) and coastal sites (2) (10). This species can also occasionally be found on the open sea near the shore or close to islands (7).

While the black swan may be found singly, it is also often seen in loose groups comprising several hundred or even thousands of individuals. When on the ground, a large group of black swans is known as a ‘bank’, whereas in flight it is known as a ‘wedge’ (7). Black swans residing in areas of suitable permanent habitat are sedentary (2) (3), while those inhabiting more temporary waters are known to be nomadic, wandering extensively in response to droughts or rainy periods (2) (3) (7).

The black swan’s diet is composed almost entirely of vegetable matter, with this species feeding on a variety of aquatic plants and algae (2), including sea grasses (10). The black swan usually finds its food by upending or by dabbling on the surface, although it is also known to graze in dry pastures and flooded fields (2).

The black swan’s breeding season appears to vary with location (2). However, it generally occurs in the wetter winter months, from February to September (7), when water levels are at their highest (2). This species nests in colonies (2) (7), and like other swans it is largely monogamous, usually pairing for life. If one bird of the pair should die, the other black swan will usually not attempt to find another mate (7).

Both the male and the female black swan take part in building the nest (7), which is a large mound of reeds, grasses and weeds that either floats on the water or is placed on the ground (2) (7). The nest is reused year on year, or is restored or rebuilt as required (7). The female black swan lays a clutch of between 4 and 6 greenish-white eggs, which are incubated for a period of 35 to 40 days (2) (7). The chicks hatch covered in light grey down (2), and are tended by both adults for a period of about six months, during which time they may ride on the backs of the adults during ventures into deeper water (7). The young black swans fledge at about 150 to 170 days old, although fledging can occur before this in years when food availability is high. The black swan reaches sexual maturity between 18 and 36 months of age (2).

Like many other waterbird species, the adult black swans lose all of their flight feathers after the breeding season, and are then unable to fly for about a month, during which time they settle on large areas of open water for safety (7).

With an extremely large range and large population size (9), the black swan is not considered to be globally threatened (2) (7). In fact, in New Zealand this species’ population is deliberately controlled through egg collecting (3).

There do not appear to be any major threats to the black swan, although short hunting seasons have been introduced in some parts of its range as a result of crop damage by this species (2) (3).

In the United Kingdom, where the black swan has been introduced, the species is still rare but has the potential to be an agricultural pest which may feed on crops and graze on and foul grass. It is also quite aggressive, and could cause problems by out-competing native wildfowl species (11).

The black swan is protected in Australia under the Australian National Parks and Wildlife Act 1974 (7).

In its introduced range in the United Kingdom, the black swan is listed under Schedule 9 to the Wildlife and Countryside Act 1981 with respect to England and Wales, which makes it an offence to release or allow this species to escape into the wild (11).